Nanoimprint lithography (NIL) is a method of fabricating nanometer scale patterns that boasts low cost, high resolution, and high throughput and has been used to fabricate devices for electrical, optical, and biological applications. As shown in FIG. 1, NIL creates patterns by mechanical pressing of an imprint resist using a template mold (or simply “template”). The imprint resist is typically a polymer formulation that is cured by heat or UV (ultraviolet) light during the imprinting process. The mold is then released, leaving a pattern in the cured resist. A pattern transfer process (such as reactive ion etching) can be used to transfer the pattern in the resist to the underlying substrate to form a wide variety of structures.
Some challenges associated with NIL are the fabrication of the template and durability of the template. High resolution template patterning is commonly performed with electron beam lithography or focused ion beam patterning. However, at smaller resolutions the throughput for these techniques can be very low. For example, an electron beam lithography method can take a significant amount of time to cover a 15 cm diameter substrate with a dense pattern of 10 nm features. Optical patterning of templates has been demonstrated, but conventional photolithography is limited in resolution to relatively large features (i.e. generally greater than approximately 200 nm feature sizes). Wear of the template can also be a significant concern in NIL. Physical contacting of the template with the resist layer during imprinting accelerates the wear of imprint templates compared to other types of lithographic masks.